Extension of the foundation to the existing foundation. Do-it-yourself foundation equipment for an extension

Various life circumstances can lead to a decision to increase your living space. Extensions can be built as a kitchen, bedroom, bathroom or other living area. The main task in this case is to choose the right type of foundation so that it is of high quality and reliable.

Choosing the type of foundation

Tape
Columnar
Pile

The first type of base for an extension is the most versatile. The strip foundation is suitable for both light and heavy structures. To avoid subsidence of the strip base, you need to apply a closed base contour.

Columnar base can be used exclusively for lightweight structures. Its advantages include extremely low cost and high reliability. The only drawback of a columnar foundation is that a basement cannot be constructed in it. The bearing base here is brick or reinforced concrete pillars, the distance between which should be from 1.5 to 3 meters.

Also, larch bars can act as pillars, but due to their fragility and high cost, this material is used extremely rarely.

If there is weak soil at the site of the planned extension and the mass of the structure is high, then it is better to use a base on piles, which can be made of steel, reinforced concrete, wood or asbestos. All piles must be tied with a strapping beam.

Features of binding the new foundation to the old

There are 2 ways to connect a new foundation with an old one:

Rigid reinforcement technology. You can use this method when the building is more than 15 years old and the foundation is well preserved. The main nuance is that there should be no heaving soils.
Expansion joint. The most inexpensive and easy-to-use method. It can be used in strip, columnar and pile foundations. For isolation, you can use roofing material.

Advantages

Rigid reinforcement:

Can be used for old buildings
Low cost

Expansion joint:

Easy to apply
Low cost
Used on any type of foundations

disadvantages

Rigid reinforcement:

Application on heaving soil is impossible

Expansion joint:

No disadvantages

Foundation for different types of outbuildings Brick extension

Before erecting a brick extension, you must choose between two types of foundations - strip and columnar. When building a veranda attached to the main house, it is not necessary to tie the foundations into a monolith, since the main building and the veranda can be of different masses.

To prevent the massive house from pulling a light extension with it, the veranda is installed on an individual foundation. At the same time, a gap of 4 centimeters must be made between the two foundations.

It is necessary to take into account the peculiarities of the soil and the massiveness of the extension. Due to the heaving soil, the extension will move during use. Lightweight foundations cannot support massive walls, so they shrink under the influence of the mass.

Additional living space can be either attached or built-in. For the first type, you will need to build an individual base with a small distance from the wall of the main building of 4 centimeters. If you do not provide a gap, then the extension will collapse over time, since its mass and the mass of the house will be different.

In most cases, for a frame construction, it is necessary to use a strip type of foundation, for the construction of which it is necessary to follow the following sequence:

Marking is made, along which a recess will be dug later
The soil from the trench is removed to the level of the lower part of the foundation of the main building. Sand is poured into the bottom of the depression, which is compacted. After the sand, crushed stone is laid, which is also compacted
Formwork is being prepared, with a height equal to the height of the future foundation. The perimeter is laid with waterproofing, and welded reinforcement is laid on the crushed stone
A concrete solution is being prepared with the following proportions - 6: 3: 1 (crushed stone: sand: cement)
The ready-mixed mortar is poured onto the 13th part of the formwork. When it hardens, the rest of the formwork height is finally poured. With the help of a vibrator, the remaining air in the solution can be removed. If this device is not available, then bubbles can be removed by simply tapping on the formwork.
The upper solidified part of the solution is leveled at one level and covered with a film material. While the solution hardens and gains strength, the upper part is periodically moistened to prevent cracking of the material.

Wooden extension

It is better to make the base for the extension made of wood from the material from which the foundation of the main building is made.

For a wooden extension, the following types of bases are used:

Tape
Columnar
Tiled

Each of these types of bases has its own characteristics and nuances, but the first type is the most popular. The way of its execution is specified above. But there is one of the small, but very important nuances - the new base must be connected to the foundation of the main structure.

Also, the choice of the place of attachment of the additional foundation to the existing one is of considerable importance.

If you plan to make a door to enter from the main building, then you can use the following method - for this you need to expand the window opening down and later insert the door. This method will help reduce costs.

In order to achieve a strong connection between two foundations, it is necessary to strictly observe the technology of erecting a new base and its docking with the main one.

To begin with, preparatory work is performed, during which:

Part of the foundation is freed, to which it is planned to make an extension
The insulating layer is removed
With the help of a puncher, 80 mm holes are made. They will help ensure a better fit between the two foundations. The more there are, the more reliable docking they will provide
Similar holes are made for reinforcement.

If there is a need for thermal insulation, then you can design a closed veranda between the entrance to the room and the street, which plays the role of a vestibule. This will prevent cold air from passing through the room. If the extension will be used exclusively in winter, the construction of the vestibule will be optional.

The choice of the foundation for the construction of the extension should be approached with great attention, since a large number of factors affect its choice. The main ones are the material from which the extension is built and the type of soil.

An error can lead to fatal consequences, in which the extension will gradually collapse or simply move along the ground. If you take into account all the above tips and tricks, then the constructed extension will serve for a very long time. Happy construction!

Is it true that the foundation for an extension is different from the main one, what are its features? Many are looking for the answer to this question, because when adding additional rooms to an existing house, you want these rooms to also have a reliable foundation. We have collected the most important tips and instructions in this article.

Everyone knows what role the skeleton plays in the human body; similar functions are assigned to the foundation. In fact, this is the basis that is responsible for the reliability and durability of the building. Also, it is the foundation that provides warmth and dryness in the room. If the base is of poor quality or does not fit the specific conditions, then dampness will appear inside, the floors may deform and completely deteriorate. It also evens out the ground level and prevents the penetration of carcinogenic gas from the soil into the dwelling.

The basis of the extension

The choice of the foundation should be especially attentive. After all, it is necessary that it freely withstand the loads and correspond to the type of soil. At the same time, you do not need to overdo it, for example, if you can fill in a strip or columnar foundation, then there is no point in replacing these simpler options with a complex monolithic base. First, it is too expensive and not worth the investment. Secondly, the first ones are much easier to perform and you can do them with your own hands even without outside help, but you will not be able to lay the concrete slab on your own.

It is mainly built of stone or concrete, but there are also wooden structures. If the construction is lightweight, then you can give preference to a shallow base located above the freezing point. But more often than not, its depth should be below this level. By designation, it is divided into carrier and combined. The latter, in addition to the standard bearing functions, must also provide seismic protection. There is also a special type, it includes "swinging" and "floating" foundations, their pressure corresponds to the pressure of the excavated soil.

What types of bases to choose from?

At this point, we will consider what types the foundation for the extension is divided into. The tape can rightfully be called universal, because it is perfect for both heavy and lightweight structures. It is located only under the external and external load-bearing walls. Basically, it is poured from concrete; to make the structure more reliable, it should be reinforced with iron bars. If you are going to do this type of foundation with your own hands, then it is better to give preference to the prefabricated version. The disadvantages include high cost.

Universal strip foundation

But the columnar, on the contrary, refers to the budget options. But it is advisable to use it only if we are talking about lightweight structures, for example, you need to tie a frame extension to a wooden house. Special pillars are used as supports, located at intervals of 1.5 to 3 meters. These pillars must be placed at the intersection of load-bearing walls. It is best to make such elements from brick or reinforced concrete, but larch beams can also be used. However, such supports are expensive, and wood is not durable.

If you are going to erect a rather massive building, while weak soil prevails, then you should give preference to the pile type of foundation. Such a structure consists of supports connected by means of a strapping beam.

How can two foundations be connected?

The foundation for the extension can be rigidly adjacent to the base of the dwelling, as a result of which a single structure is formed. Such a solution is relevant if the site has a weak or not heaving type of soil. It is also worth giving preference to this option when you are going to make an extension of several floors and want to connect it to the main house through a single roof.

If the base is a slab, then a monolithic foundation should also be poured for additional housing. In this case, it is necessary that its thickness is at least 400 mm or the base of the residential building has protrusions. In this case, the slab reinforcement can be welded to the frame of the new foundation. In addition, if you wish, you can do everything yourself.

Monolithic foundation slab

The tape-to-tape connection assumes the presence of a sand cushion and reinforcement with a longitudinal slot. Metal rods are driven into specially prepared holes in the base of the house and form a frame for the new foundation. Further, the joint is made by means of a release with a length of about 40 cm.

You can also build a separate base for the extension, which will be in close proximity to the house. A sheet of roofing material should be placed between the two bases. This material acts as an excellent waterproofing, you can also place a layer of thermal insulation, or you can do with a simple tow. In this case, it is very important that this layer allows the new base not to collect water during precipitation and not damage the foundation of the house. From the outside, special decorative overlays are fixed to the wall, covering the seam.

Laying the foundation - we do it according to science

Now let's move on to the practical part and consider how to make a foundation for an extension with our own hands. This detailed instruction will help you save on the services of a master, because it is designed for independent construction work.

Do-it-yourself foundation for an extension

How to make a foundation for an extension to a house - a step by step diagram

Step 1: choosing a base

The new foundation must fully correspond to the type of the old foundation. In addition, the load and soil type are taken into account. For example, if we are talking about a massive extension to a brick house, then it is necessary to lay a tape or make a pile foundation. But if the additional room is adjacent to a wooden dwelling, then it is possible to get by with a cheaper columnar option.

Step 2: Calculations

Regardless of whether you give preference to a rigid type of connection or a separate base, the depth and width, as well as the dimensions of the base pillars, if any, should be the same as the foundation of the house. Determining these parameters is quite simple. It is necessary to dig a hole next to the wall of the housing and measure the dimensions of the base. If there should be no questions about how to measure the depth of the structure, then in order to measure the width, you should take a rod, bend one edge of it 90 ° and push it horizontally under the foundation. Then we turn the rod until its bent part rests against the back side. After that, you need to make a mark on the bar and pull it out. By measuring the distance from the hook to the mark, we know the width.

Step 3: preparatory work

Before pouring the foundation for the extension, it is necessary to carry out preparatory work. If you decide to give preference to a rigid connection, then we dig a trench of a given size and drill a hole in the already existing base. Moreover, their diameter should exceed the thickness of the reinforcement. You should also prepare metal rods. It is necessary to make a longitudinal slot at their end and insert a special wedging insert into it.

Step 4: shaping the framework

We drive the reinforcement with wedges into the prepared holes. The number of rods is taken at the rate of 20 pieces per square. Thus, the frame of the future foundation is formed. To ensure a reliable connection of the following parts, it is necessary to leave the edges of the reinforcement with a length of about 300 mm, which will subsequently need to be welded.

Step 5: Formwork installation

Now you need wide wooden planks. We form the formwork of the specified dimensions. We securely fix its walls by means of supports, earth, cinder block, etc. You can close the inside of the formwork with polyethylene. The latter is especially true if you are pouring only part of the foundation and you have to reuse these boards.

Step 6: pouring the mortar

We prepare a mixture of cement, sand, gravel and water. It is very important to keep the proportions correctly. For example, for M300 you can take 10 kg of cement, 30 kg of sand, 40 kg of crushed stone, mix everything well and pour 40 liters of water. If the concrete turns out to be too dense, then you should dilute it with liquid, but only add it in small portions so as not to spoil the solution. We pour concrete into the formwork and wait a few days until it completely hardens. Moisten periodically, otherwise cracks may appear.

Step 7: shaping the columnar foundation

It is important to make such a base when a lightweight extension is adjacent to a wooden house. We drill wells so that they are below the level of soil freezing. We form a sand cushion and install fiberglass reinforcement. This material has excellent properties and does not need additional treatment with waterproofing compounds. Also, a formwork of a given size is formed and poured with concrete. This foundation for an extension is the easiest to implement, and everyone can create it with their own hands.

Step 8: erect a separate foundation

But when the number of storeys of the main and adjacent housing is different, then a separate foundation should be made in close proximity to the previous one. The distance between the two bases ranges from 2 to 5 cm, depending on the number of storeys in the new building. The higher it is, the wider the seam is selected. We fill this gap with thermal insulation materials or tow. Then a special decorative overlay is attached to the wall of the house. In this case, it is very important to correctly mark the base. To do this, we pull the cord on pegs along the perimeter of the future site and check if the diagonals are equal. If a heaving type of soil prevails on the site, then the floor of the extension must be made so that it is not lower than the flooring of the main housing by the amount of possible deformations.

The foundation for the extension is an important stage in the construction of the entire structure. The main thing here is not to harm the main building. Therefore, it is possible to make a reliable foundation with your own hands, but the basic technological nuances of construction should be observed.

Determining the type of base

An extension is an independent structure. It can be laid simultaneously with the construction of the main building. In this case, there will be no inconvenience when joining the two parts on which the house and the attached part will stand. However, most often the need to expand the living space arises after a long operation of the house. In this case, new walls have to be added to the existing structure. And it is very important to follow all the rules and build the foundation for the extension of the house so that later, due to the deformation of the base, the house does not warp and it does not crack.

To make the foundation correctly with your own hands, you need to find out the following:

determine what base is used under the house and at what depth it lies;
find out the styling features (if on columns, then what is the width of the column spacing, and if the base is of the tape type, then what is the width of its sole);
determine the nature of the soil and find out the depth of soil freezing.

Typically, data about the house is described in the technical documentation. But if the building is not very new and no documents have been preserved, then you can determine what the building stands on as follows:

dig a hole at the base of the house in the place where there will be an abutment;
find out what lies in the basics and check if there is a sand cushion;
determine the materials from which the previous foundation is made, and other parameters;
see what the soil is in terms of the degree of heaving.

Tip: In order to find out the width of the old strip base when building an extension to an existing house, you need to pass a metal pin with a hook at the end over it. Turning the pin down, find out the stop point and fix the mark. Taking out the rod back, you can find out the width of the old base by the mark.

What types of connections are there?

Taking into account the peculiarities of the old base, a method of adhesion to the main house is chosen. There are several possibilities to make the connection of the two bases:

in the form of a rigid connection with reinforcement - it is used when the house is stable, does not shrink and allows the construction of a common foundation with the main structure;
Expansion joint connection diagram
base for an extension using an expansion joint - in this case, a separate base is made that does not have a strong connection with the main structure. It is often used when the main structure is made of foam blocks, and the extension is planned to be made of a heavier material.
With expansion joint

A single requirement for any option is that the depth of laying a new one should be equal to or slightly less than the old base in order to make it possible to make shrinkage painlessly.

Where does the first option apply?

Foundations can be rigidly connected if:

the house has a strip base;
the annex is made to a brick house and brought out under a common roof with it;
the new plinth is cast in one piece with a shallow strip foundation.
Scheme with a strip shallow foundation

Work progress

On a rigid hitch

In the absence of heaving soil and with an established foundation of the main house, a foundation is made for an extension on a rigid hitch. For this you need:

Determine the size and depth of the old base.
Dig a trench no deeper than the previous level.
Drill holes in the foundation of the old house for laying reinforcing rods (the hole is drilled to a depth equal to 35 times the diameter of the reinforcing bar).
Calculation of fastening on a rigid hitch
Cut the required number of reinforcement rods per 1 sq. M. 20 rods when laying a closed loop. An open loop is made with individual needs calculations.
Drive rods with washers welded to the ends into the holes.
Make a formwork by placing reinforcement there.
Pour concrete.
Contour diagram

In this way, with your own hands, you can tie the extension to any type of structure.

Where is the second type applied?

According to the second type, you can build a foundation for an extension to the house, if you want to connect parts from different materials. For example, make a veranda from foam blocks to a wooden house. Or from foam blocks to a brick house.

Such a foundation for an extension to an existing house is separate, laid next to the old building and connected with an expansion joint. It is not difficult to do this with your own hands, you just need to correctly connect the joints, sealing the seam with heat-insulating moisture-resistant materials - for example, roofing material and ordinary tow.

Work progress:

Dig a trench according to the recommendations above.
Attach boards covered with waterproofing material to the existing base. This will be the deformation layer. In general, the size of the gap to the existing base is 5 cm, but for a small building, a 2 cm gap is sufficient.
Pour concrete tape. If the attached part is on the pillars, then it is required to fill in the pillars, and then make an expansion joint in the same way.
attachment of an anchorage on a foundation on pillars
Fill the gaps in the seam with heat-insulating materials (foam, tow, etc.)
Seal the seam with any sealant and hide the joint with a decorative trim strip.

Pile-screw method

This is a good and quick way for light annexes made of wood, foam blocks and other materials; if there is a rigid and reliable grillage, it can also be used for heavier structures.

The method is good because it is performed quickly, does not destroy the existing foundation and can be used on any type of soil, including heaving and swampy. In addition, any structures made of different materials can be installed on piles without any problems, including bricks, wooden beams, foam blocks, etc.

Foundation on pillars

A very common method, suitable for structures made of foam blocks, wood, OSB and other lightweight materials. Poles-supports are installed at the rate of 6 pieces per extension measuring 7 m by 3 m.

Progress:

dig holes under the pillars to the depth of freezing;
lay a sand pillow at the bottom of the pits;
install fiberglass reinforcement (you can also metal, pre-treated with a composition for waterproofing);
install the required formwork on the aboveground part.
concreting the pillars on the formwork.

How do you choose the best option?

It makes no sense to make a serious foundation for a small veranda or other lightweight structure, say, from foam blocks or OSB. It is quite enough to use pile-screw supports. An extension made of foam blocks will normally stand on a shallowly recessed strip base. When building a heavy structure, you must also choose an appropriate reliable base.
How to make a foundation for a house from FBS blocks with your own hands? How to make a hole in the foundation for a hole for air circulation?

The basis of any structure must have a reliable and solid foundation. The durability and safety of the house depends on this. Before starting construction work, it is necessary to calculate all the values and mark the foundation, taking into account the type of soil. Foundation marking is the transfer of a project from a drawing to a construction site, taking into account the scale of the structure.

Necessary tools for work

To carry out the transfer of the house plan (extension) to the site, you will need:

roulette;
pegs (metal, wooden);
cord or rope;
protractor;
nails and screws;
plumb line;
hydro level.

You can mark the foundation yourself, the main thing is to accurately determine its corner points and maintain the corners of the house and its future extensions.

Popular methods of marking the foundation

Golden triangle method... This method consists in determining the location of one wall, which is one of the legs of the triangle. The remaining structure is determined by the proportion of its sides 3: 4: 6.
Spider web method. It is typical for this method to correctly calculate the perimeter of the house (extension) and take a construction cord of the required length. Pegs are fixed on the site, the diagonals of the structure are determined and the cord is pulled.
Curved line intersection method... The first wall is traced from the top of the base corner. We measure equal distances from the point of the bar, mark the marks, describe arcs of equal radius. The intersection point will be perpendicular, i.e. adjacent wall of a house or annex.

Step-by-step instructions for the foundation marking of the outer and inner contours

The first thing to start with is to determine the location of the structure and the depth of the base, all these data are included in the documentation of the building. According to SNIP, the recommended depth of soil freezing is 1.5 meters. If the soil is sandy, you can make the depth shallower. If the soil is clay, the depth of the base should be at least the recommended rate.

Important! When the soil freezes, the soil rises, there is pressure on the base of the house, due to which it can rise and deform. If you want to do all the work with high quality, explore the soil of the land.

Outer contour. To correctly display the outer line of the base, we recommend driving the first peg into the lowest corner. Parallel to it along the frontal line, a distance equal to the length of the base is laid. In the same way, we lay a length perpendicular to the base segment deep into the site. As a result, you should end up with an angle of 90 degrees. To prevent errors, you can apply the Pythagorean theorem, according to which, in a triangle with sides 3, 4, 5, the angle between the smallest sides is considered right. In practice, the theorem is applied as follows, they take 12 m of a construction cord, divide it by 3 m from the beginning and 4 m from the end of the starting point, fix the 3 m mark with a peg.

The cord is installed on the marking line, and 4 m is placed perpendicular to it, after which the cord is connected to the beginning. The remaining sides are marked in the same way. If the base is rectangular, you can check that the foundation is laid out correctly. The correctness of the form is measured by the diagonals, if they are equal to each other, then the markings are applied accurately. If the base is of a complex shape, it is necessary to divide it into squares and measure their diagonals. This way you should have 4 corner base pegs and a future base position.

Expert advice! For accurate marking of the foundation, you can use a level or a homemade triangle.

Inner contour the bases are displayed after the external markup. With the help of a peg, mark the inner border of the structure. It is installed at a distance of 40 cm from the outside. If there are structural walls in the project, they are applied to the surface in the same way. The correctness of the delimitation of the walls is checked by the equality of the diagonal.

Note! With a slab base, you can use the external marking method. With a strip base, it is necessary to carefully carry out all calculations of the inner perimeter of the structure and the width of the foundation strip.

Strip foundation marking

Method number 1. According to the plan of the future house or extension, determine the position of the main point of the right corner, drive in a peg. Observing the level, measure the length of one of the sides with a tape measure, drive in 2 pegs and pull the cord tight. So you should get one side of the structure, measure the other side using the same principle. The result should be a rectangle. A level will help you set a right angle, and a tape measure will help you measure the exact length.

Method number 2. Drive in the peg in the right corner according to the principle of method # 1. Using a tape measure and a level, measure the length of the front wall, fix with a second peg. On the string of the second peg, mark the length of the left wall. Mark the points of the remaining walls in a square and add their values, and from the resulting value, calculate the root. Secure the length to the cord and secure it to the right peg. Pull 2 ropes in these places, connect them at the marked points, drive in a peg at the point of contact, which will be the 3rd corner. Calculate the 4th angle in the same way.

Advice! It is possible to achieve the correct transfer of the strip foundation and the delineation of the house plan (extension) using the golden triangle method.

The strip base is made in the form of underground and continuous walls, crossed reinforced concrete beams. Its width is calculated from the quality of the soil, as a rule, it is 50 cm, i.e. equal to the average width of the walls.

Pile foundation marking

For the correct marking of the pile or columnar foundations, it is necessary to define a rectangle and check the correctness of its shape. Install pegs for future piles in the corners, determine the position of additional supports throughout the entire area of the site. As a calculation, take 1.5-2 m between adjacent piles.

Consequences of incorrect markup

Any error in the marking of the foundation can affect the entire construction process and the structure as a whole. Of the adverse consequences, it is worth noting:

the complexity of the construction of the walls of the house and the extension;
the formation of a skew of the building;
destruction or deformation of the building;
shortening the life of the house or extension;
problems in the construction of the roof;
the inability to install rafters and wall strapping;

You can do the correct transfer of the house plan to the site with your own hands, the main thing is to take into account the scale, size and adhere to rectangularity.

Thanks to the experience of professionals, the process of marking the site can be facilitated and done with the help of the following tips:

the thread should be tightened firmly, without sagging, pulling out the peg; the damaged thread will not give the exact dimensions of the base;
pegs can be made independently from the remnants of reinforcement, they are perfectly installed in the soil and firmly fixed;
always focus on the outer boundaries of the land and on the project of the house or extension;
do not remove the threads until all work is completed;
use professional devices whenever possible;
if you are not confident in your abilities, seek professional help.

Sooner or later, many suburban real estate owners decide to increase the living space by adding an extension to the house. In order for the connection of the main house to the extension to occur without problems, it is important to achieve a reliable and durable connection of the bases. As practice shows, there are two main ways to attach the foundation of the extension to the already existing base of the house:

rigid connection using reinforcement;
expansion joint.

Each of the options for connecting the main foundation with the base of the extension has its own characteristics and nuances, which should be considered more thoroughly.

Most often, the rigid connection of the foundation of the main building to the extension is used on soils that are not subject to heaving. Most often, this method is used in the process of low-rise construction in situations where the extension is functionally connected to an existing building and is located with it under a single roof.

To make the base for the extension, a special hole is drilled in it to a depth of about 35 cm. Its diameter should be equal to the diameter of the reinforcement that will be used for driving. If the construction of the extension is carried out according to a scheme that assumes the estimated length of the reinforcement is greater than the width of the foundation, holes in the base of an existing house are drilled only for a part of the width. In this case, the reinforcement is mounted according to the anchor principle.

If the contour is planned to be closed, the holes should be made at two levels and in a checkerboard pattern. As for the reinforcement, it must necessarily have an anchor wedging at one end and a welded washer at the other.

A rigid connection is also used in situations where the house has a recessed strip base, and the construction of an extension is planned from monolithic reinforced concrete.

A foundation with a rigid base can be in two versions:

tape-tape;
plate-plate.

When installing such a foundation, it is assumed that the following list of works will be performed:

dig a trench, the depth of which corresponds to the already existing foundation of the main building;
fill the bottom of the trench with sand (create a sand cushion) and tamp;
drill holes in the base;
drive reinforcing rods with a longitudinal slot into pre-prepared holes;
insert a wedging insert (for example, made of wood) into the slot of the reinforcement;
drive the reinforcement into the holes in the corners of the base;
to form the frame using the remaining extract from the reinforcement that has already been driven in (for this purpose, parts with a length of 300 to 400 mm are specially left;
after making the frame, fill the base tape with concrete;
wait until the concrete is completely dry.

In order to attach a foundation to a house, you will need a whole list of equipment. First of all, we are talking about the following tools: shovel, building level, reinforcing bars, sand, wood inserts, a mixture of concrete and boards for the manufacture of formwork.

Foundation with expansion joint

An extension to a house of a foundation with an expansion joint is most often used in the field of industrial, as well as multi-storey construction. That is, where the soils under the structure can differ significantly in their deformation properties. For example, quite often an extension of another number of storeys is connected to an existing house of one storey by laying a foundation with an expansion joint.

In any case, the expansion joint must necessarily be provided at the design stage of construction.

At its core, any expansion joint, through which the foundation for another structure is connected to the house, is a heater in the gap between the basement floors and the walls. Often, ordinary tow is used as this insulation. The place where the connection with the house is made is fenced off with a special decorative overlay, which is attached to the house wall.

In the conditions of building a house on heaving soil, the floor level of the extension is recommended by experts to be below the floor level of the main structure. The magnitude of the drop should correspond to the indicator of the expected deformations.

In order to attach a foundation to an existing house using an expansion joint, the following significant points should be taken into account:

Leave a small gap between the main house and the foundation of the extension (no more than 5 cm). In order to comply with the indicated requirement, before starting the laying of the base, boards should be attached to the foundation of the house, pre-treated with waterproofing material. In the future, it is they who will perform the function of the expansion joint assigned to them.
In a one-story construction, the thickness of the expansion joint can be no more than 2 cm.
If desired, the expansion joint can be filled with any heat-insulating material. Most often, penoplex, as well as polystyrene, are used for this purpose. Outside, everything is covered with a decorative overlay.

If the main purpose of an extension to an existing house is to form a separate zone, and not to expand an existing room, a rigid connection of two bases between one house and another should not be done in any case, since the consequences may be the most undesirable. In this situation, it is much more advisable to use an expansion joint.

If we are talking about a small extension, it can be erected on a shallow strip foundation or a foundation on piles.

Choosing the type of foundation for the extension

Experienced experts strongly recommend using the type of foundation that was used for the construction of the main building for the construction of the extension. This is due to the fact that different bases react differently to contact with the soil and also react differently to the shrinkage of the building.

Accordingly, if the main house is built on a strip base, and the extension is built on columnar piles, sooner or later the auxiliary structure will collapse. Thus, on such things as connecting foundations, one should not economize under any circumstances.

If you are planning to connect a building to a home, you can use a variety of bases. Most often, we are talking about the following options:

Strip foundation

For those who decided to use a strip foundation for an extension, the following list of works will need to be completed:

make markings in parallel with tracing at the construction site of the base structure (this will require wooden pegs and an ordinary rope);
dig a trench along the marking;
fix the reinforcement;
prepare a trench;
fill up a sand cushion (approximately 100-120 mm) and carefully tamp the bottom of the trench;
lay a waterproofing film;
install reinforcement structure;
fill the trench with a solution of cement and gravel.

The casting of the strip foundation should be approached as responsibly as possible. It is better to do the work in several passes. As the first layer, one third of the trench is poured, and after drying, one second. The technology, in principle, allows the use of foam blocks, but not in all cases.

After the complete drying of the cement-gravel layer, the formwork is built. The formwork is poured to the brim with concrete. After laying, the concrete is pierced simultaneously in several places. This prevents air bubbles from forming. After complete drying of the concrete, the formwork is removed.

And finally, just before the walls are erected, the almost complete structure is covered with a layer of waterproofing material. Most often, roofing material, tar, liquid rubber or bitumen mastic are used for this purpose.

Column foundation

If your plans include the construction of a small and lightweight house, the use of a columnar foundation is quite acceptable. It is usually made of either concrete or brick. For a medium-sized building, 6 support pillars are most often enough.

For the device of such a base, you will need:

dig a hole (below the level of soil freezing);
pour a sand pillow on the bottom;
install metal (or fiberglass) fittings;
to process the reinforcement with moisture-proof material (for metal reinforcing rods);
install the formwork;
pour the base with concrete.

The construction can be started immediately after the concrete hardens. If it becomes necessary to increase the parameter of the height of the pillars, you can put a brick on top of the concrete.

Foundation on screw piles

The foundation on screw piles is the simplest and most budgetary type of foundation. It should be understood that it is only designed for structures that are not too heavy, since it cannot support a lot of weight. But if you are going to attach a wood veranda to the house, this option is fine.

In most cases, this type of foundation does not require the participation of specialists. Even a person with no experience in construction is quite capable of screwing in screw piles with his own hands. Probably, it is for this reason that many people opt for a foundation on screw piles.

If the base on the piles is installed correctly, it can last for a long period of time.

But no matter what foundation is required to be installed, on screw piles, columnar or some other, the most important thing is that all work is performed in accordance with the technology. Therefore, if you do not have enough construction experience, it would be most advisable to entrust the pouring of the base to experienced and qualified specialists.

Over time, the owner of a private house or summer house may need to expand the total area of home ownership. The extension to the house is a full-fledged part of it. The construction of the extension begins with the construction of the foundation. Before you start pouring the foundation for the extension with your own hands, you need to go through several stages of building the foundation.

Selecting the type of foundation

The type of foundation is determined based on the total weight of the extension, the composition of the soil base, the depth of freezing and the level of groundwater. Consider the main types of foundation structures.

Strip foundation

Based on the depth of the foundation, they are divided into shallow and deeply buried.

Shallow foundations are intended for houses made of lightweight structures, in the absence of the threat of heaving of the soil. The shallow foundation is a monolithic reinforced concrete beam on a sand cushion with a continuous reinforced belt. When erecting such a foundation, a drainage device is mandatory.

The sole of a deeply laid foundation is located below the freezing depth in order to avoid deformations from heaving of frozen soil.

Concrete strip foundation by its design can be monolithic, prefabricated and combined.

Reinforced concrete tape monolith is the strongest and most reliable base.

The prefabricated base is erected from ready-made reinforced concrete blocks, beams and slabs.

Combined structures are built from prefabricated factory blocks and concrete. This type of foundation is used with a complex configuration of a house in terms of plan.

Columnar foundations

Columnar supports are brought under light extensions. The pillars are placed in all corners of the base plan, at the junctions of the bearing walls and at the points of concentration of loads. The distance between the centers of the pillars is 1.2 to 2 meters. Between the supports from above, a strapping is made (reinforced concrete or metal randbeams), connecting the entire structure into a single support system.

The laying of pillars brings significant savings in materials compared to a strip monolith.

Pile foundations

For outbuildings, screw piles are sometimes used. Screw piles are metal pipes with coarse threaded threads or blades at the lower end. The process of installing supports is like screwing a screw into a tree.

The advantage of installing such a base is its quick installation, which does not require excavation and concrete work.

Bored piles

A reinforcement cage is inserted into the drilled holes in the ground and poured with concrete. Such supports are called bored piles.

The complexity and high cost of the work determine the advisability of using bored piles on loose and fluid soils, where the installation of other foundation foundations is impossible.

Slab foundations

The foundation slab is made in the form of a monolithic platform or from crossing monolithic strips. Such foundations are erected on all types of soils. A monolithic reinforced concrete slab is a structure with powerful spatial rigidity. On uneven, highly compressible soils, only this type of foundation is laid.

The advantage of a monolithic reinforced concrete slab is its versatility, reliability and independence from the groundwater level.

Such a base structure is not used on terrain with a slope of elevation difference of more than one meter.

Preparation for pouring the foundation

After the owner of the house has opted for one or another type of foundation, he does the axial marking of the base of the extension with his own hands. Then they carry out excavation work, the device of a sandy, crushed stone cushion. A waterproofing layer is placed on the pillow in the form of two layers of roofing material or one layer of a polymer film.

The width of the trenches and the outer boundary of the pit should be wider than the foundation as much as it would allow the installation and dismantling of the formwork to be carried out without hindrance.

The formwork can be made of wooden panels, metal panels and other materials. Carefully check whether the verticality of the walls of the formwork, the reliability of fastening stops, clamps, spacers, ties and other fasteners are correctly maintained. Correctly aligned formwork must not have gaps. Carefully examine all joint seams. If gaps wider than 4 mm are found, then they are immediately closed.

Any leakage of concrete from the formwork can significantly weaken the foundation. Correctly executed geometry of the fence allows the difference in the lengths of the diagonals between opposite corners of the formwork no more than 20-30 mm.

Before pouring concrete, check the integrity of the waterproofing surface. The inner space of the formwork is cleaned of debris and foreign objects. The installed reinforcement frame should not come into contact with the formwork surface. To do this, special clamps are installed in the places where the reinforcement elements mate with the fence.

Preparation of concrete mix for pouring

In order to correctly fill the formwork, the developer needs to organize the process of preparing the concrete mixture and its continuous supply to the unloading points. Watch the video on how to properly prepare the concrete mix.

If an extension of small dimensions will be erected by hand, then depending on the volume of concrete work, you can install one or two concrete mixers. In the case of a very small base size, you can get by with a construction trough or any suitable container and improvised tools.

The owner of the house needs to know what brand of concrete he will prepare with his own hands. Therefore, it is necessary to prepare a supply of cement, sand, solid filler (crushed stone, gravel) and a container with water. Determine how many materials are required for one batch.

Pouring the foundation for the extension

Consider the process of pouring concrete into the formwork of a strip foundation for an extension with our own hands.

Filling should be done by at least three workers. The ready-mixed concrete is loaded into the formwork in layers with a thickness of 200 mm. Each layer is compacted with a manual vibrator or, in the absence of such, rammed with a piece of reinforcement or a similar device. They are rammed until "cement milk" appears on the surface of the concrete. Under the influence of a vibrator, concrete is evenly distributed throughout the entire volume of the formwork, allowing air to escape. Watch the video on how to fill a foundation strip.

If we assume the presence of air cavities in the concrete body, then this will entail a loss of the bearing capacity of the foundation and the appearance of deep cracks in it.

Pouring is carried out continuously and at a time. A break in work can be allowed, but not more than two hours.

Curing

Properly organized care of hardening concrete will not allow the monolith to lose its bearing capacity due to increased evaporation of moisture from the concrete surface or freezing of the base mass for the extension.

In the summer, the concrete is covered with a moisture-proof material and periodically moistened.

In winter, measures are taken to heat both the side surfaces of the formwork and insulate the upper surface of the concrete.

Do I need to combine the foundations of the house and annexes

The owner of the house definitely needs to know what type of base is near his house, what grade of concrete was used for pouring, what quality the soil base of his dwelling has. If the owner of the house is not the first, then he may not know anything about the state of the foundation. Then, if possible, you need to dig a small hole at the site of the foundation and analyze the nature of the foundation, the depth of its foundation, the amount of its settlement over the entire period of operation of the building.

For example, a house stands on a strip-type reinforced concrete foundation - shallow. The sediment for all the years of the structure's existence is insignificant.

In this case, the foundation of the extension is laid, similar to the base of the house. At the junction of the bases, the ends of the old monolith are exposed and connected to the annex with the bare reinforcement of the old tape. The extension and the house will behave like a single, solid structure.

When laying a free-standing monolithic strip base, it is necessary to arrange expansion joints, both at the junction of both foundations, and along the entire transverse perimeter of the connection of the extension structures and the house.

They also do the construction of other types of foundations.

If you own a suburban real estate, then you probably thought about increasing the living space at least once. There is not always the financial ability and strength to acquire a new house or rebuild it, the way out may be to increase the area of an existing building. With any such construction, the most important stage is the creation of a high-quality base for the extension.

Design features

If you are thinking about the question of how to make a foundation for an extension to a house, then you should listen to the opinion of experts who advise you to form the foundation of the same structure as the foundation of the main building. This is due to the fact that different foundations can interact with the soil in their own way, which can cause different shrinkage. Therefore, do not economize and build reliable identical foundations. Before making the foundation for an extension to the house, you must choose one of the three existing ways to connect the bases. The first provides for the formation of a monolithic foundation, which will be connected by thick metal reinforcement. The second method involves the construction of independent foundations, between which the expansion joint will be located. The third technology is a screw-pile foundation. Before pouring the base, it is necessary to take into account what the severity of the extension will be and what characteristics the soil has.

Perfect for a building that has been in operation for several years and has not shrunk due to the uniform soil. Otherwise, it is recommended to make a separate foundation by connecting it to the main one using an expansion joint. Regardless of which method of creating the foundation was chosen, it should be buried just as much as the base of the main house was buried. Sometimes the foundation is placed slightly higher, taking into account the shrinkage.

Foundation on rigid reinforcement

If you are faced with the task of how to make a foundation for an extension to a house, then you can create a foundation on rigid reinforcement that is suitable for an established house. The shrinkage of the latter at the start of construction work must be completed. This design is not suitable for heaving soils.

Methods of work

Initially, it is necessary to measure the depth and dimensions of the old base, only after that you can start preparing the trench. Its depth should not be greater than the depth of the foundation. In the old base, holes are made with a diameter slightly larger than the diameter of the reinforcement. The depth of the holes should be determined by the following formula: for this, the diameter of the reinforcement should be multiplied by 35. If the width of the base is not enough for the hole, then the reinforcement must be hammered, for this a longitudinal cut is made at the end, and then the wedging inserts are installed. This technique is quite reliable.

Working with fittings

If you are thinking about how to make a foundation for an extension to a brick house, then the above method is perfect. To do this, calculate the number of rods. For a closed loop of a new structure, about 20 elements are most often required for each square meter of the foundation. The components are cut with an angle grinder or using an emery machine. If we are talking about an open circuit, then the number of reinforcing rods can be determined individually, depending on the width of the future foundation. The rods should be installed in the drilled holes, but before that, washers are welded to their ends.

Quite often, home craftsmen are interested in how to make the foundation for an extension to a house. Increasing the room will allow this to be done. Speaking of the above, it should be noted that further actions provide for the creation of formwork, into which the reinforcement is laid. The resulting space is poured with concrete. Then the solution is left until it hardens completely, after which the master can begin construction work.

Cases of using rigid foundation joints

Rigid docking is used when the extension is united by a common roof with the main building, as well as in the presence of a strip foundation. This method of connecting the bases is also used when the building is installed on a columnar foundation, and the fastening is carried out on a plinth. This indicates that this element must have the required height and width. Rigid joining of two structural elements can be used in the presence of a tape type, when it is included in one monolithic type system.

Formation of a separate foundation

Before making the foundation for it, you must take into account that the most popular and simplest way is to build a separate foundation. In this case, the foundation will be located quite close to the main building, and an expansion joint should be installed between the structures. The function of the layer is to protect the structure from deformation and cracking during shrinkage. To form a seam, it is necessary to use a moisture-resistant heat-insulating material, tow or roofing material. Considering that the structure will still shrink, the foundation should be laid above the finished one.

Work technology

If you are thinking about how to make the foundation for an extension to the house, it is recommended to consider the photo in advance. They will allow you to understand which technology is the best to carry out the work. The gap between the new and the old foundation when forming a separate foundation should be 5 centimeters. Before the start of concreting, boards covered with a layer of waterproofing are applied to the finished base. In the future, these elements will play the role of an expansion joint. If there is a small extension on one floor, a seam with a thickness of 2 centimeters will be enough. The filling of the resulting space can be carried out with a heat-insulating material, which is quite often penoplex or foam. And you can close the gap with a sealant that is resistant to weathering. Outside, everything can be masked with a decorative overlay.

The foundation for an extension to a house from blocks can be created using this technology, since it is the most acceptable.

Creating a columnar foundation

If the extension is supposed to be formed from light materials like wood, then an inexpensive foundation on pillars would be the best option. If the dimensions are limited to 7x3 meters, then it is enough to prepare 6 support pillars. It will be necessary to drill a well in the soil, going deeper below the level of soil freezing. A sand cushion is placed on the bottom, fiberglass reinforcement is installed, and then the formwork of the required size is placed. The resulting hollow space should be poured with concrete, and if it is necessary to increase the height of the supports, red brick masonry should be made.

Base on piles

When professional builders are thinking about how to make a foundation for an extension to a house, they most often resort to the method of forming a foundation on screw piles. This is due to the fact that this design is the cheapest and easiest for lightweight buildings. One disadvantage is susceptibility to corrosion, but this can be excluded by the method of anti-corrosion treatment. Installation work can be carried out as soon as possible; after the completion of the work, it is permissible to proceed with further construction. For a small object, the supports can be screwed in on their own, which will reduce the cost of work.

Concrete preparation

Before you make the foundation for an extension to the house with your own hands, you should ask how the concrete is properly mixed. The success of further work will depend on its quality. The darker the color of the cement, the more reliable and stronger the mixture will be. If you have not yet encountered the mixing process, then you must remember the correct sequence for placing the components in the concrete mixer. Initially, there is water, then crushed stone, sand and cement are laid. Consistency must be observed in order to achieve uniformity in the composition. While all the components are being mixed, the concrete mixer should be turned on, but during the rest of the equipment motor, you can measure the ingredients and bring them up for subsequent kneading.

Conclusion

If you are faced with the question of how to make a foundation for an extension to a house from blocks, then you can use the above recommendations. They require the use of appropriate mechanical equipment for mixing the mortar. This will exclude the formation of a seam between the poured layers.